A 400 base pair region in SV40 contains the promoter elements of early and late transcription and the origin of DNA replication. We have identified a surrogate TATA box that lies 30 base pairs upstream of the 5' start site of late transcription that functions in vitro and in vivo to regulate the level of late transcription. The level of early transcription is effected by GC rich sequences and their distance from the TATA box that lies upstream of the early 5' start site.